Hey there I'm starting to work on my thesis and this is one possible subject. I'm reading a few papers (pretty much anything that appears on the first google search page) dealing with it from several different angles. From a completely general and mathematical stand to specific examples, like the Borel resummation ambiguity in the double well and how instantons relate to that. But I haven't found anything on this forum about it. In fact, besides a few papers here and there I haven't found much at all. So I thought I'd ask here if anyone worked with this or is working right now, and has some advice to give. BTW, I didn't know where to put this topic, here or in Quantum Mechanics.